Mineral Test Borings A geologist believes that the
probability that the rare earth mineral dalhousium occurs in the
Greater Toronto region is 0.001. If dalhousium is present in that
region, the geologist’s test borings will have a positive result 90%
of the time. However, if dalhousium is not present, a negative
result will occur 80% of the time.
(a) If a test is positive on a site in the region, find the probability
that dalhousium is there?
(b) If a test is negative on such a site, find the probability that
dalhousium is there?